n. The movement of a plant (or other organism) either towards or away from water
the GNU version of the Collaborative International Dictionary of English
n. A tendency towards moisture.
n. In a broader sense, any curvature or turning induced in certain growing plant organs under the influence of moisture.
The Century Dictionary and Cyclopedia
n. A state induced in a growing organ by the influence of moisture, in which under certain conditions it turns toward the moisture, and under other little understood conditions it turns away from the moisture.
Word Usage
"This is in response to positive hydrotropism ( "water-turning" G)."